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Newsgroups: info.grass.user
Path: zorro.cecer.army.mil!shapiro
From: shapiro at zorro.cecer.army.mil (Michael Shapiro)
Subject: Re: histogram in r.support
Message-ID: <C25DF1.B2t at news.cecer.army.mil>
Sender: news at news.cecer.army.mil (Net.Noise owner)
Organization: US Army Corps of Engineers Construction Engineering Research Labs
References: <9302052030.AA02522 at mtqgrass.ESD.ORNL.GOV>
Date: Mon, 8 Feb 1993 20:40:13 GMT
Lines: 36

In <9302052030.AA02522 at mtqgrass.ESD.ORNL.GOV> hnw at mtqgrass.ESD.ORNL.GOV (Bill Hargrove) writes:

>Hello GrassHoppers:

>     When I ask r.support to build a histogram for a raster image, does it
>perform a contrast stretch, or does it just record the histogram
>distribution of the cells as they currently exist?
>                                            Thanks,
>--------------------------------------------------------------
>  ___                   
>  /  )      /  /      /  /                          
> /--<   o  /  /      /--/ __  __  __  __  _      _       
>/___/__<__/__/__    /  /_(_<_/ <_<_/_/ <_(_)_\/_(/_     
>                                  /  
>                               <_/
>--------------------------------------------------------------
>Bill Hargrove
>Oak Ridge National Laboratory
>Environmental Sciences Division
>P.O. Box 2008, M.S. 6038
>Oak Ridge, TN  37831-6038
>(615) 574-1902
>(615) 576-8646 (fax)
>hnw at mtqgrass.esd.ornl.gov
>--------------------------------------------------------------

It just builds a file with the histogram in it, not contrast stretch
is done. Mostly you don't need the histogram.
The only program which I think looks at this is i.composite.
If you want to create a contrast-stretched grey scale color map for
an image, use r.colors [map] color=grey.eq
-- 


Michael Shapiro U.S. Army CERL
Environmental Division